| Year | Count |
|---|---|
| 1971 | 5 |
| 1972 | 7 |
| 1973 | 6 |
| 1974 | 10 |
| 1975 | 8 |
| 1976 | 12 |
| 1977 | 50 |
| 1978 | 45 |
| 1979 | 56 |
| 1980 | 42 |
| 1981 | 65 |
| 1982 | 32 |
| 1983 | 30 |
| 1984 | 25 |
| 1985 | 34 |
| 1986 | 22 |
| 1987 | 24 |
| 1988 | 12 |
| 1989 | 6 |
| 1990 | 26 |
| 1991 | 14 |
| 1992 | 18 |
| 1993 | 27 |
| 1994 | 17 |
| 1995 | 25 |
| 1996 | 29 |
| 1997 | 22 |
| 1998 | 64 |
| 1999 | 46 |
| 2000 | 63 |
| 2001 | 233 |
| 2002 | 138 |
| 2003 | 99 |
| 2004 | 71 |
| 2005 | 71 |
| 2006 | 38 |
| 2007 | 53 |
| 2008 | 37 |
| 2009 | 23 |
| 2010 | 7 |
| 2011 | 17 |
| 2013 | 6 |
| 2016 | 10 |
| 2018 | 5 |
| 2019 | 16 |
| 2020 | 10 |
| 2021 | 14 |
| 2022 | 10 |